This invention relates to prefilled, readily activated syringes. More particularly, this invention relates to a means for activating a prefilled, readily activated syringe which requires a minimum amount of effort and provides positive activation.
The type of syringe concerned with this invention is described in U.S. Pat. Nos. 3,378,008 and 3,376,866. In these patents, a threaded engagement is effected between the stopper in a vial and the syringe body which activates the syringe by means of a central cannula member which will pierce through the stopper vial as the vial is threadably moved over the piercing cannula. This type of threaded activation poses problems in that time must be spent turning the vial prior to activation. Further, if the vial is carried on the syringe by partially engaging the threads, premature activation could occur as it is difficult to determine how far to thread the vial onto the syringe without piercing the vial stopper. Consequently this syringe unit is marketed with the vial separated from the syringe body. This means that additional time must be utilized to activate the syringe because the two components must be threaded together prior to activation. Automatic type activated syringes are disclosed in U.S. Pat. Nos. 3,320,955; 3,330,279 and 3,825,003. All of these particular units utilize spring tensioning means in order to activate the cannula and drive it through a piercing stopper. These particular mechanisms are costly to manufacture as are the screw-type means for accomplishing the same purpose as described in U.S. Pat. No. 3,115,135 for the purpose of engaging a cartridge as well as a piston member to form a disposable syringe. However, nowhere in the prior art is there indicated the utilization of expandable finger members which can engage in a positive manner a groove or resistance means in one position on the hub of a piercing cannula member to prevent accidental puncture yet also afford positive puncture when the cannula is moved to another position to engage additional resistance means or a groove.
It is an advantage of the present invention to provide a prefilled, readily activated syringe which affords quick and positive activation; a readily activated syringe which can be fabricated from a minimum number of parts; a prefilled, readily activated syringe which provides cannula alignment and prevents nonrotation and positive movement of the piercing cannula with a minimum amount of effort; a prefilled, disposable readily activated syringe which is easily molded and at a minimum amount of cost.